Topic 4: Uveal Tract Flashcards
Briefly describe the uveal tract
it is made up of IRIS, CILIARY BODY, CHOROID
it is a Continuous structure
has two openings: pupil and optic nerve canal
- Describe the iris and its properties
divided into the CILIARY zone and PUPILLARY zone
the two zones are separated by the thickest part of the iris, COLLARETTE (2mm from the periphery)
iris diameter: 10-12mm
pupil diameter: 1-8mm
thinnest part of iris: ciliary margin/iris root
gets its colour from melanocytes
state the structures of the iris from anterior to posterior
(1) anterior border layer
(2) stroma (sphincter muscle)
(3) iris pigmented epithelium (dilator muscle)
explain the structures of the iris
(1) ABL - anterior most, provides colour to iris (melanocytes)
(2) stroma - contains connective tissue, blood vessels (MAC), pigment cells, home to SPHINCTER muscle encircling pupil
(3) PE - posterior most, double layered, double pigmented, home to DILATOR muscle (APE) arranged radially in ciliary zone
explain sphincter vs dilator muscle (pupillary actions)
sphincter: contracts to constrict the pupil/miosis, parasympathetic pathway
dilator: contracts to dilate the pupil/mydriasis, sympathetic pathway
they are antagonistic muscles, when one contracts the other will relax
explain blood supply to iris
Major arterial circle (found in iris stroma near iris root, towards ciliary body) - 2 LONG posterior arteries & 7 ANTERIOR ciliary arteries
branches to also form minor arterial circle in pupillary zone
explain nerve supply to iris
Trigeminal nerve (CNV) & oculomotor nerve (CN3) for pupillary actions
- Describe the ciliary body and its properties
it is 5-6mm ‘band’ surrounding the iris
extends from scleral spur (where sclera starts) anteriorly to ora serrata (where CB ends, choroid starts) posteriorly
divided into two zones: pars plicata & pars plana
explain pars plicata vs pars plana
pars plicata: anterior region of CB towards the iris, contains ciliary processes, inner NPE site of aqh production
pars plana: flatter than plicata, posterior region of CB towards the choroid
both contain all 3 layers of CB
State the ciliary body structures from outer to innermost
(1) ciliary muscle
(2) stroma
(3i) outer pigmented epithelium
(3ii) inner non pigmented epithelium
explain the ciliary body structures
(1) ciliary muscle - helps with accommodation
(2) stroma - highly vascularised (MAC), connective tissue, anteriorly continuous with iris stroma, posteriorly continuous with choroid stroma
(3i) outer pigmented epithelium - continuous with anterior iris epi & transforms posteriorly into retinal pigment epi
(3ii) inner non pigmented epithelium - continuous with posterior iris epi & transforms posteriorly into neural retina
explain blood supply to ciliary body
Major arterial circle (found in CB stroma, near iris root) - 2 long posterior arteries & 7 anterior ciliary arteries
explain nerve supply to ciliary body
trigeminal nerve (CNV) & oculomotor nerve (CN3) for accommodation
- describe choroid
thin, soft brown tissue
it lines the inside of the sclera
posterior most uveal structure
extends anteriorly from CB to optic nerve posteriorly
state the structures of choroid from outer to innermost
(1) supra choroid
(2) choroidal stroma
(3) choriocapillaris
(4) bruch’s membrane
